Lewitt LCT 040 MATCH stereo pair

Problems appeared when trying to use these beautiful designed mics on the Zoom F6 field recorder. Hiss and whistle sounds appeared when turning the volume up, too bad too ignore. I tried to eliminate the problem by changing channels, cables and surroundings. Nothing helped. I contacted Lewitt, and they did send me a new pair of mics, which was really very nice of them. The new ones showed similar symptoms. I then read in a review that some old interfaces show problems with these mics due to their relatively high power consumption, and the old interfaces too weak phantom power supply. The Zoom f6 field recorder is a new model which works usually very well, but perhaps it has a similar problem? All my other 10 mics run perfectly on it. Finally I got the Lewitt LCT 040 mics running ok and without the hiss on a Behringer interface, but to be honest, their ordinary self-noise seems to be the highest of all cheap mics I own. This is not mentioned in most of those flattering reviews that made me buying them. No problem when recording a punk or metal concert, but quieter music? The positive: They have a clear and fresh sound, unexpected nice proximity effect but to my taste, a bit too hyped in the higher frequencies. The clamps and the stereo bar that followed the package are really nice and I will use and love them as if their where my own, but the mics are of no use for me. They do not work clean on my preferred equipment, the Zoom F6 recorder I am using the most.